You can view the slideshow gallery in full screen by clicking the outward arrows button on the right of the filmstrip controls (bottom of the slideshow). This will enable you to view the pictures in entirety. To see title and description, click on the picture.
You can also configure many slideshow characteristics during fullscreen mode to suit your viewing pleasure. The main configuration hub is in the Options menuat the top right of the screen with the following features:
To view pictures in their normal dimensions, uncheck the option Embiggen small things to fit screen.
To have picture information visible throughout the slideshow, check the option Always show title and description.
To change the speed of the slideshow transition, toggle between the slow, medium and fast radio buttons.
To exit fullscreen mode, press the inward arrows button on the right of the filmstrip controls (bottom of the slideshow).